sublimehighRule

Attachment: JavaScript file with suspicious base64-encoded executable

JavaScript attachment or compressed JavaScript file containing a base64 encoded executable.

MITRE ATT&CK

T1566.001 T1204.002 T1486 T1036 T1027 T1059

defense-evasionexecution

Detection Query

type.inbound
and any(attachments,
        (
          .file_extension in~ $file_extensions_common_archives
          or .file_extension in ("js", "jar")
        )
        and any(file.explode(.),
                (
                  (
                    .file_extension in ("js", "jar")
                    or any(.flavors.yara, . == "javascript_file")
                  )
                  and any(.flavors.yara, . == 'base64_pe')
                )
        )
)

Data Sources

Email MessagesEmail HeadersEmail Attachments

Platforms

Raw Content

name: "Attachment: JavaScript file with suspicious base64-encoded executable"
description: "JavaScript attachment or compressed JavaScript file containing a base64 encoded executable."
type: "rule"
severity: "high"
source: |
  type.inbound
  and any(attachments,
          (
            .file_extension in~ $file_extensions_common_archives
            or .file_extension in ("js", "jar")
          )
          and any(file.explode(.),
                  (
                    (
                      .file_extension in ("js", "jar")
                      or any(.flavors.yara, . == "javascript_file")
                    )
                    and any(.flavors.yara, . == 'base64_pe')
                  )
          )
  )

attack_types:
  - "Malware/Ransomware"
tactics_and_techniques:
  - "Evasion"
  - "Scripting"
detection_methods:
  - "Archive analysis"
  - "File analysis"
  - "YARA"

id: "b8db0cf3-1708-5fd0-b0f3-ee23a06505ca"